Numerous pharmaceutical substances are available for administration to animals, including humans, for a variety of purposes. These substances include, for example, therapeutic agents, such as drugs; dietary supplements, such as vitamins; prophylactic agents, such as antigens for use in vaccines; and diagnostic agents, such as labeled imaging agents. Administration of these substances can be via a number of routes including intramuscular, subcutaneous and oral administration. Intramuscular or subcutaneous administration of the substance suffers from disadvantages: relatively specialized skills are required to administer the pharmaceutical; large scale administration can be difficult to perform; it is expensive; and a number of side reactions can occur to the substance administered. Many antibiotics (i.e., tetracycline and penicillin), and hormones (i.e., progesterone and estrogen) can be administered successfully via the oral route.
There are, however, biologically active agents, for example certain dietary supplements, drugs, hormones and immunogens, whose efficacy is almost totally lost upon oral administration. Included among those agents that cannot be effectively orally administered are polypeptide agents, such as Calcitonin, Erythropoetin, Granulocyte Colony Stimulating Factor, Stem Cell Factor, Granulocyte Colony Stimulating Factor, LHRH analogues, Somatostatin, Insulin, Interferons, Plasminogen Activator Inhibitors and species of DNA and RNA. Oral delivery of certain protein and polypeptide drugs is complicated by the presence of proteolytic digestive enzymes in the stomach and intestines. Unprotected proteins, which are administered orally, are largely degraded by such enzymes before they are able to pass through the enteric wall and enter blood circulation. To some extent this effect can be overcome by the administration of extremely large doses of the pharmaceutical agent. This approach, however, is not economically feasible for many pharmaceutical agents and may result in undesired side effects.
Thus, there continues to be a need for the development of compositions and methods for convenient delivery of such substances to animals, including humans, efficiently. Accordingly, among the objectives herein, it is an objective to provide compositions and methods for convenient delivery of agents to be delivered to a subject.